B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Oral vs. Intramuscular Vitamin B12 in Vitamin B12 Deficiency The Blood Project Optimal Vitamin B12 Dosage and Treating Deficiency Vitamin B12 injections deliver high doses of this essential vitamin directly into your bloodstream for better absorption than oral supplements to boost energy, support red blood cell production and maintain nerve function.